1. Field of the Invention
This invention relates to a magnetic recording element and a magnetic memory preferably usable for a Random Access Memory (RAM), and magnetic recording methods utilizing the magnetic recording element and the magnetic memory and methods for fabricating the magnetic recording medium and the magnetic memory.
2. Description of the Prior Art
Conventionally, a semiconductor Random Access Memory, (semi-conductor RAM) composed of a given semiconductor memory is mainly utilized as a Random Access Memory (RAM). If such a semiconductor RAM is used under severe condition, the stability may be deteriorated. The trend of the deterioration in stability becomes conspicuous as the semiconductor element is miniaturized.
Therefore, such an additional process as refresh operation, where a given current is flown to maintain data and thus, realize the stable operation, is required in a semiconductor RAM such as a dynamic Random Access Memory (DRAM). In another semiconductor RAM not requiring such an additional process, the access time is prolonged.
In this point of view, recently, an attention is paid to a Magnetic Random Access Memory (MRAM) utilizing a magnetic recording element. In the MRAM, a signal of xe2x80x9c0xe2x80x9d or xe2x80x9c1xe2x80x9d is recorded in accordance with the direction of the magnetization. Since the magnetization direction is not changed only if an external magnetic field is not applied to the MRAM, the data stored in the MRAM is maintained remarkably stable.
A magnetic recording element such as having a GMR (giant magneto-resistive) film or a TMR (tunneling magnetoresistive) film is proposed for the MRAM. In such a magnetic recording element, however, since the magnetic properties such as MR ratio is not satisfied sufficiently, which are required to read out data of xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d, a practically usable MRAM is not realized.
It is an object of the present invention to provide a new magnetic recording element practically usable for a MRAM and a magnetic memory utilizing the magnetic recording element.
It is another object of the present invention to provide magnetic recording methods utilizing the magnetic recording medium and the magnetic memory, and methods for fabricating the magnetic recording element and the magnetic memory
For achieving the above object, this invention relates to a magnetic recording element comprising:
a first magnetic film to generate spin vortex by an external magnetic field, and
a second magnetic film, on the first magnetic film, having a magnetization at the center thereof substantially perpendicular to the surfaces thereof.
The inventors had intensely studied to develop a new magnetic recording medium practically usable for a MRAM. As a result, they found out that such a magnetic recording medium can be obtained so that a first magnetic film to generate spin vortex by an external magnetic field and a second magnetic film having the magnetization at the center thereof perpendicular to the surfaces thereof are stacked.
FIGS. 1 and 2 are structural views showing a magnetic recording medium according to the present invention. A magnetic recording medium 10 shown in FIGS. 1 and 2 includes a first magnetic film 1 to generate spin vortex by an external magnetic field and a second magnetic film 2 having the magnetization C perpendicular to the surfaces thereof which is formed on the first magnetic film 1. Herein, the magnetization of the second magnetic film 2 is varied from the perpendicular magnetization at the center to the longitudinal magnetization at the periphery thereof, which is not shown. In addition, an insulating layer 3 is formed between the first magnetic film 1 and the second magnetic film 2 to control (repress) a current through the magnetic recording medium 10.
When an external magnetic field is applied to the first magnetic film 1 forward and then, a spin vortex is generated in the direction A, a given vertical magnetization is generated in the direction B at the center of the spin vortex. On the other hand, when an external magnetic field is applied to the first magnetic film 1 backward and then, a spin vortex is generated in the direction D, a given magnetization is generated in the direction E which is opposite to the direction B.
In FIG. 1, the magnetization B of the first magnetic film 1 and the magnetization C of the second magnetic film 2 are parallel and in FIG. 2, the magnetization B of the first magnetic film 1 and the magnetization E of the second magnetic film 2 are anti-parallel. Therefore, much current is flown on the condition that the magnetic state as shown in FIG. 1 is satisfied than on the condition that the magnetic state as shown in FIG. 2 is satisfied.
Therefore, if data of xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d are recorded in accordance with the magnetization direction of the first magnetic film 1, the magnetic state can be read out as the amount of a current through the magnetic recording medium.
That is, in the magnetic recording element of the present invention, magnetic recording is performed on the magnetization direction of the spin vortex of the first magnetic film, and magnetic reading is performed on the amount of a current through the magnetic recording element which depends on the direction of the spin vortex of the first magnetic film as in the same manner in a conventional MRAM. Therefore, a new structural MRAM can be obtained from the magnetic recording element according to the present invention. A magnetic memory according to the present invention is constructed so that plural magnetic recording elements according to the present invention are arranged on a given substrate. A practical MRAM is composed of such a magnetic memory according to the present invention.
Herein, the term xe2x80x9cspin vortexxe2x80x9d means a magnetization state vertically generated in a film. Several preferred embodiments of the magnetic recording element and the magnetic memory will be described hereinafter. Also, magnetic recording methods utilizing the magnetic recording medium and the magnetic memory, and methods for fabricating the magnetic recording element and the magnetic memory will be described hereinafter.